Investigations are being conducted into the biochemical composition of the sensory retina, pigmented epithelium, choroid, and biological fluids in normal and disease states, particularly in animal models of human retinal degenerations and in human retinal diseases. The tissue-specific distributions of inorganic constituents are studied by flameless atomic absorption, with concentrations of Cu, Zn, and Ca of particular interest. These elements are being assayed in 24-hour urine specimens from patients with retinal degenerations (retinitis pigmentosa and macular degenerations). The effects of nutrition and genetic background on the progress of chorioretinal degeneration in the retinal dystrophic pigmented RCS rat are being investigated. Age of onset and incidence of posterior subcapsular cataracts and the history of proression of mature cataracts are being studied in both pink-eyed and black-eyed retinal dystrophic RCS rat models of retinal degeneration-related cataract. Nutritional and environmental factors involved in incidence and prevention of the cataracts are being investigated.